Voided Biaxial Concrete Slab System
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Voided Biaxial Concrete Slab System

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Voided Biaxial Concrete Slab System

The concept of voided biaxial slab system is to replace the nom-working concrete in the slab with voids. The immediate results is optimization of concrete up to 35% reduction in the slab self-weight while still providing a high equivalent stiffness. This will enhance the bearing behavior on the whole structure elements. 
Any voided biaxial slab system consist of two elements:

1- The void formers.
Which have a flattened rotationally symmetrical shape. Void formers are made of plastic material and have different heights and shape according to the structural design.
 
2- Steel cage.
Used to integrate void formers and make spacing between them. Steel cages are positioned between the bottom and top reinforcement layers in the slab’s cross section where they also serve as supporting cages.



Multiple void sizes can be provided for a wide range of slab thickness depending on span requirements and load applied. These can be used in concrete structure for various types of projects such as commercial, residential, parking, and institutional building as well as other applications.

- Voided biaxial slab differ in three ways from traditional solid flat plate slabs.

1- Reduced dead load due to the concrete displacement of void formers. The bending moments and column reactions are reduced consequently.


2- Reduced stiffness of the slab due to the presence of the void formers. The deflection of the slab is influenced consequently.


3-Reduced shear capacity of the slab due to the presence of the void formers. This requires the identification of the slab areas with too high shear in which the void formers must not be placed.



- Void biaxial slab system advantages.

  • No drop panels or drop beams are needed in 90% of cases.

  • Slab can be 35% lighter than solid slabs or 20% lighter than post tension slabs.

  • Quick system, overlapping is possible. Different slab construction works (shuttering, bottom steel, forms distribution, MEP, top steel) can be done at the same time in different parts of the slab by using construction joints, spilt levels, etc. in void biaxial slab, full-slab same-stage work, end to end is not a must.

  • Easy during construction changes. Elements can be easily removed or canceled, if so, required due to MEP or any other last-minute change at site.

  • No outriggers. Voided biaxial slab system does not need outriggers for tensioning which for other systems usually requires between 10% to 20% of extra shuttering.

  • Less props, about 35% less than solid slab and 15% to 25% lighter than post tension slabs.

  • After construction flexibilities, cut-outs or coring is possible exactly as in solid slab.

  • No problem with possible future change of use such as smaller imposed loads or different loads distribution.

  • Up to 20% less earthquake design load.

  • No future maintenance needed.

  • Improved fire resistance and acoustic insulation.

  • Optimized concrete and steel reinforcement quantities in slabs, columns, and footing.

  • Saving in implementation cost, including labor, formworks, scaffolding and time.

  • Do not require skilled workers to assemble them. The system could be done by ordinary labors of the general contractor, no need for special trained staff or waiting specialized subcontractor.






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